Howdy,
couple of suggestions:
1) check through your key bindings and joystick axis assignments once, then check again. I always seem to miss things. Sometimes my rudder pedals get assigned as yaw, thrust and roll, so when I press on my right pedal I get all sorts of aerobatic manoeuvres.
2) I have the TM Warthog, and have discovered in 1.5ob that if I have either engine switched to Motor the APU will not start successfully, which in turn means I can't start the engines as the APU is required to achieve a start. Potentially some switching arrangement is preventing your engines from starting?